Well at the local level (especially with the White Sox) - these stations really could not afford to use tape stock and archive games. NBC doesn't have that excuse.

Boston was an exception as every game televised from 1972 on exists - the Red Sox paid the stations to do it.

Really? They have never shown/aired any of them at least from the 70s. After 40 years you begin to wonder what they are saving them for if they sit on a shelf and collect dust. Why save them if you are never going to do anything with them???